A probe card is used in semiconductor wafer fabrication and/or packaging facilities to test the integrity of every semiconductor chip (or die) produced. The process of testing involves testing equipment referred to as “probers” and an interface device that couples the testing equipment to the die to be tested. The interface device is commonly known as a “prove card”. The probe card generally comprises a large number of probes, which take the form of pins. The pins are arranged on a printed circuit board, or other support structure, in a pattern that corresponds to the layout of the bonding pads on the die to be tested. Each die requires a probe card with a pin pattern that is specific to the layout of the bond pads on the die.
Test signals are exchanged between the prober and the die via the probe card and in particular, the pins that contact the bond pads on the die to be tested. The quality of signals received by the prober from the die is dependent on the quality of the probe card and the quality of contact between the pins and the bond pads on the die.
Conventional probe cards comprise a number of cantilevered probes fixed by epoxy resin to a ceramic or aluminium retaining ring. Typically, the free end of each cantilevered probe (ie the tip which contacts the bond pad) is overhanging the retaining ring by approximately 5 mm to 6 mm and there is an average pitch (ie spacing between the tips) of between 80 μm to 200 μm.
However, as chip geometries and resulting bond pad pitches are getting smaller and smaller (currently about 50 μm) it is becoming increasingly difficult to design and build probecards using conventional cantilever pin designs.
Therefore, in order to achieve smaller probe pitches, smaller diameter wire is being used to manufacture the probes. However, using thinner wire has the disadvantage that the probes are substantially weaker and the overhanging cantilevered design of the probes makes them susceptible to lateral deflections at the tip. Therefore, the tips can not reliably maintain the correct x-y position. This has the risk that the tip may not contact the correct bond pad on the die during testing, resulting in the prober possibly giving an incorrect test result.